New Self-Healing Material Activated by Light
Schematic of the new material repairing itself.
CREDIT: Marc Pauchard of Adolphe Merkle Institute, Case Western Reserve University, U.S. Army Research Laboratory
"Just add light." This simple instruction could someday be on the label of a new material that repairs itself when exposed to ultraviolet light.
The new material, detailed in this week's issue of the journal Nature, is a long polymer chain made up of lots of smaller molecules with sticky ends that act like glue to bind to one another . When light strikes the polymer, the molecules become unglued, turning the once solid material into a soup of small molecules that flows like a liquid and can fill in cracks.
"Ultraviolet light is absorbed by the sticky end groups of our new supramolecular polymers, converted into heat, and the supramolecular structures disassemble into the small building blocks from which they were made," said study co-author Christoph Weder, a professor of polymer chemistry and materials at the University of Fribourg in Switzerland.
The alterable material could be turned into self-repairing automotive paint and floor varnishes, as well as indestructible plastics , like the kind found on rubber watchbands.
The self-healing material isn't ready for commercial use, and Weder said it will "be a while" before it lines the shelves of hardware stores.
Self-healing polymers aren't new, but most of them require heat to trigger the repair process. The problem with this approach is that it's difficult to isolate the heat to the damaged area.
"By using light, we have more control over the process … since light can be applied very locally, that is, only in the vicinity of a defect," Weder explained. "This leaves the other portions of an object untouched, so it can continue to serve its function while the damaged portion is healed."
The new healable substance also has environmental benefits.
"Damaged plastics are typically dis¬carded in landfill or in some cases repaired with a manually applied patch," write Nancy Sottos and Jeffrey Moore, both of the University of Illinois, Urbana, in an accompanying Nature article.
"Healable poly¬mers offer an alternative to the damage-and-discard cycle and represent a first step in the development of polymeric materials that have much greater life spans than currently available materials."
The researchers made and tested several polymer recipes to find the one with the best mechanical strength and fast healing. While they've found materials that repair themselves with only short exposure to the UV light (less than a minute), they're still tweaking the formulation to make the polymers stronger and stiffer.
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